content: import java.util.*;
  import java.io.*;
  import java.lang.*;
  
  class Node{
          int data;
          Node next;
          Node(int x){
              data=x;
              next=null;
          }
      }
    
  class Test { 
      
      public static void main(String args[]) 
      { 
          Node head=new Node(15);
      	head.next=new Node(10);
      	head.next.next=new Node(12);
      	head.next.next.next=new Node(20);
      	head.next.next.next.next=head.next;
      	if (isLoop(head)) 
              System.out.print("Loop found"); 
          else
              System.out.print("No Loop"); 
      } 
      
      static boolean isLoop(Node head) 
      {   Node temp=new Node(0);
          Node curr=head;
          while (curr != null) {  
              if (curr.next==null)
                  return false;
              if(curr.next==temp)
                  return true;
              Node curr_next=curr.next;
              curr.next=temp;
              curr=curr_next;
          } 
          return false; 
      }
      
      public static void printlist(Node head){
          Node curr=head;
          while(curr!=null){
          System.out.print(curr.data+" ");
          curr=curr.next;
      }System.out.println();
      }
  } 